1. Field
Embodiments relate to a reliability evaluation circuit and a reliability evaluation system that are used to evaluate reliability of a plurality of unit devices corresponding to a stress voltage. More particularly, embodiments relate to a reliability evaluation circuit and a reliability evaluation system that can apply a plurality of stress voltages having different voltage levels to a plurality of unit devices, and rapidly determine reliability of the unit devices corresponding to the applied stress voltages.
2. Description of the Related Art
Reliability of an integrated circuit (IC) is determined by predicting not only when the IC operates under a normal conditions, but also when the IC operates under abnormal conditions. Here, the normal condition means a condition in which a power and a signal having an optimal strength and magnitude are applied to the IC. Abnormal conditions includes conditions in which a voltage level of power applied to the IC is higher or lower than that in the normal condition. Here, the IC is a circuit that is embodied in a semiconductor device so as to perform predetermined functions or a semiconductor device having the circuit.
The IC includes unit devices, such as a transistor, a capacitor, a resistor, and metal-lines having a plurality of different line widths. The IC may further include an inductor. Thus, it is necessary to determine reliability of the IC by considering reliability of each of the transistor, the capacitor, the resistor, the inductor, and the plurality of metal-lines.
In general, reliability of the IC is evaluated in developments of processes applying to the IC. However, in order to assure stability of a corresponding process while products are manufactured, evaluation of reliability is generally performed on the corresponding process in which products are manufactured. Evaluation of the reliability may include resistance evaluation corresponding to a stress voltage for transistors having different ratios of a gate length to a gate width, capacitors having different areas, thicknesses, and materials of insulators, resistors formed of different materials, inductors, and metal-lines having different line widths. In order to rapidly evaluate reliabilities of the unit devices, an accelerated life test (ALT) may be conducted. At this time, reliability of each unit device is evaluated by applying a stress voltage having a voltage level higher than a voltage level used in a normal operation. When the stress voltage is applied to each unit device for a predetermined time period, and the voltage level of the stress voltage is varied, the reliability of each unit device corresponding to the stress voltages having various voltage levels may be evaluated at the same time.